Embattled Internal Revenue Service official Lois Lerner sent official documents from her government e-mail address to a personal account, according to House Oversight Committee chairman Darrell Issa and his colleague, Ohio congressman Jim Jordan.

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“This raises some serious questions concerning your use of a non-official e-mail account to conduct official business,” the GOP lawmakers wrote in a letter to Lerner demanding all documents from her non-official account for the period between January 2008 and the present. “Additional documents related to the Committee’s investigation may exist in these non-official accounts over which you have some control, and the lack of access to this information prevents the Committee from fully assessing your actions,” they explained. Issa and Jordan are requesting that Lerner produce the documents by August 27.

The use of personal e-mail accounts to conduct government work also has the potential to impede federal-records requests by the public because personal accounts are not archived by the government. Controversy erupted, for example, over former EPA administrator Lisa Jackson’s use of a government account under the name Richard Windsor which, like a personal account, would not be captured by records requests relating to Jackson.

Lerner, the former director of the IRS’s Exempt Organizations unit, was placed on administrative leave in late May after refusing to resign her post. She invoked her Fifth Amendment rights in testimony before the Oversight Committee and has yet to speak at length about her knowledge of the IRS’s targeting of tea-party groups. E-mail correspondence recently unearthed by the House Ways and Means Committee shows Lerner exchanging messages with an FEC attorney about two conservative groups; one tax-law expert told National Review Online that the information she disclosed about one group constitutes a felony.

Congressional investigators have not yet called Lerner back to testify; she is demanding immunity in exchange for her testimony.